Constituent concentration measuring apparatus and constituent concentration measuring apparatus controlling method

a technology of concentration measuring apparatus and constituent concentration, which is applied in the direction of instruments, applications, diagnostic recording/measuring, etc., can solve the problems of not getting satisfactory results so far in the blood sugar level measurement of the living body, and achieving the effect of improving the measurement accuracy

Active Publication Date: 2012-12-11
NIPPON TELEGRAPH & TELEPHONE CORP
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Benefits of technology

[0361]In the noninvasive constituent concentration measuring apparatus and constituent concentration measuring apparatus controlling method according to the invention, when the photoacoustic signal emitted following irradiation of the liquid or the test subject with the intensity-modulated light is detected to measure the constituent concentration, the modulation frequency at which the light is intensity-modulated is swept in a range where the acoustic wave detection means possibly shows the resonant high sensitivity, and the photoacoustic signal is measured at the frequency where the modulation frequency matches the resonance frequency of the acoustic wave detection means. Therefore, the constituent concentration set as the measuring object can correctly be measured.
[0362]In the noninvasive constituent concentration measuring apparatus and constituent concentration measuring apparatus controlling method according to the invention, the two light beams having the mutually different wavelengths are intensity-modulated at the same frequency, the liquid or the test subject is irradiated with the intensity-modulated light beams to measure the photoacoustic signal generated in the liquid or the test subject. Therefore, the unevenness on the frequency characteristics of the acoustic wave detection means does not have adverse influence. In addition, the modulation frequency at which the light is intensity-modulated is swept in the range spanning the resonance frequency of the acoustic wave detection means which is possibly changed, and the photoacoustic signal is measured at the frequency which matches the resonance frequency of the acoustic wave detection means. Therefore, the detection is hardly affected by the external influence, and the measurement can correctly be performed.
[0363]In the constituent concentration measuring apparatus and constituent concentration measuring apparatus controlling method according to the invention, the photoacoustic signal is detected under the environment of the acoustic impedance which is substantially equal to the acoustic impedance of the object to be measured or the test subject, so that signal attenuation can be minimized. The attenuation is caused by the boundary reflection between the test subject and the surroundings thereof, as well as by the contact between the test subject and the acoustic wave detection means. Furthermore, the decrease in sound collection efficiency of acoustic wave detection means and the decrease in accuracy of the photoacoustic signal can also be prevented.
[0364]According to the invention, the arrangement in which the positional relationship between the photoacoustic signal generation source and the acoustic wave detection means becomes optimum is searched for. Thus, the constituent concentration can be measured by detecting the photoacoustic signal in the optimum arrangement in which the scatterers such as a bone has little influence.
[0365]Furthermore, the photoacoustic signal is detected in the arrangement in which the signal intensity of the detected acoustic wave becomes the predetermined value, so that the constituent concentration can be measured without influence of the many parameters associated with a change in placement of the constituent concentration measuring apparatus.
[0366]Furthermore, the influence of the pressure pressing the test subject is reduced by pressing the acoustic wave detection means against the test subject with a constant pressure.

Problems solved by technology

However, the interaction between the glucose and the electromagnetic wave is weak, there is a limitation to intensity of the electromagnetic wave with which a living body can safely be irradiated, and the living body is a scatterer for the electromagnetic wave.
Therefore, satisfactory result is not obtained so far in the blood sugar level measurement of the living body.
However, the sufficient accuracy is not obtained.

Method used

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  • Constituent concentration measuring apparatus and constituent concentration measuring apparatus controlling method
  • Constituent concentration measuring apparatus and constituent concentration measuring apparatus controlling method
  • Constituent concentration measuring apparatus and constituent concentration measuring apparatus controlling method

Examples

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Effect test

first example-1

[0819]In the blood constituent concentration measuring apparatus according to the first embodiment shown in FIG. 1, it is effective that a laser light source is used as the first light source 101 and the second light source 105. In selecting the laser light source, it is necessary to estimate the necessary output laser power level.

[0820]In irradiating the human body with the light, there is the acceptable limit of the light intensity. Generally one-tenths of the intensity in which affection is generated in 50% individual is defined as the maximum tolerance in JIS C6802. According to JIS C6802, the maximum tolerance is 1 mW per 1 mm2 in the continuous irradiation of non-visible infrared light (wavelength 0.8 μm or longer) for the skin.

[0821]In a first example, the blood constituent of the measuring object is set at blood sugar, the irradiation light wavelength is set at 1.6 μm, and the modulation frequency f is set at 150 kHz or more because of the above-described principle. The wave...

first example-2

[0845]In a first example-2, for the purpose of the improvement of the acoustic coupling state, an acryl plate having the thickness of 6.6 mm is formed in the same diameter of 10 mmφ as that of the ultrasonic detector 513 in order to cause the acoustic coupler 512 to be a resonance type. One of the surfaces of the acoustic coupler 512 is attached to the ultrasonic detector 513 through vacuum grease, and the other surface is in contact with the living body test region 510 through the acoustic matching gel.

[0846]In the above configuration, as a result of the two-time measurement in the same procedure, the measured values of the photoacoustic signal s2 are 150 μV and 153 μV, and the measured value of the difference signal s1−s2 between the photoacoustic signals is 59 nV. In the above measurement, the time constant of the phase sensitive amplifier 514 is three seconds. The glucose concentration M of 3.4 mM (61 mg / dl) is determined from the measured values.

first example-3

[0847]In the first Example-2, the resonant frequency does not completely coincide with the modulation frequency f in the acoustic coupler 512. Therefore, in a first Example-3, during measuring the forestage photoacoustic signal s2, the frequency of the oscillator 503 is swept in a range of several percent to operate the two-phase type phase sensitive amplifier 514 in the R-θ mode, and the modulation frequency f is set such that the output of the signal output terminal 515 becomes the maximum. Therefore, in the acoustic coupler 512, the resonant frequency is caused to completely coincide with the modulation frequency f.

[0848]Through the same procedures as the first Example-2 except for the above procedure, 600 μV and 604 μV are obtained by the two-time measurements. The measured value of the difference signal s1−s2 between the photoacoustic signals is 0.25 nV. In this case, the time constant of the phase sensitive amplifier 514 is one second. The glucose concentration M of 3.6 mM (65...

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Abstract

An object of the present invention is to provide a noninvasive constituent concentration measuring apparatus and constituent concentration measuring apparatus controlling method, in which accurate measurement can be performed by superimposing two photoacoustic signals having the same frequency and reverse phases to nullify the effect from the other constituent occupying large part of the object to be measured. The constituent concentration measuring apparatus according to the invention includes light generating means for generating two light beams having different wavelengths, modulation means for electrically intensity-modulating each of the two light beams having different wavelengths using signals having the same frequency and reverse phases, light outgoing means for outputting the two intensity-modulated light beams having different wavelengths toward a test subject, and acoustic wave detection means for detecting an acoustic wave generated in the test subject by the outputted light.

Description

TECHNICAL FIELD[0001]The present invention relates to a noninvasive constituent concentration measuring apparatus and constituent concentration measuring apparatus controlling method, particularly to the noninvasive apparatus and method in which glucose of a blood constituent is set as a measuring object to measure a concentration of the glucose, i.e., a blood sugar level in a noninvasive manner.BACKGROUND ART[0002]Various methods are proposed to date as the noninvasive constituent concentration measuring method based on percutaneous irradiation of electromagnetic wave and / or observation of radiation. In these methods, an interaction between the objective blood constituent, for example, a glucose molecule in the case of a blood sugar level, and the electromagnetic waves having a particular wavelength, i.e., absorption or scattering is utilized.[0003]However, the interaction between the glucose and the electromagnetic wave is weak, there is a limitation to intensity of the electromag...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): A61B5/1455A61B5/00A61B5/145G01N21/00G01N21/17G01N29/00G01N29/24
CPCA61B5/0095A61B5/14532A61B5/1455G01N29/2418A61B5/6838G01N21/1702G01N29/2425G01N29/449A61B5/6826A61B5/1495
Inventor NAGANUMA, KAZUNORITAJIMA, TAKUROOKABE, YUICHISUDO, SHOICHI
Owner NIPPON TELEGRAPH & TELEPHONE CORP
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